This invention relates to engines for rotating a drive shaft and more particularly to such an engine in which the cylinders and axial movement of the associated reciprocating pistons are parallel to the longitudinal axis of the drive shaft.
Heretofore, so-called wobble plate and swash plate mechanisms for reciprocating piston engines have been provided in which the cylinders of such engines have been arranged in a parallel relation to a drive shaft. In such engines, the translatory reciprocating movement of the pistons within the cylinders has been converted to a rotational movement for rotating an axle or drive shaft by the utilization of an inclined rotating disc connected to a shaft with the inclined rotating disc engaged eccentrically from linkages driven from the longitudinal axial movement of the pistons thereby to rotate the disc and associated shaft which is operatively connected to the drive shaft for rotation thereof.
However, such wobble plate mechanisms for reciprocating piston engines have been connected directly to the connecting rods for the pistons and have been axially aligned with the longitudinal axis of the main drive shaft for converting the reciprocating movement of the pistons to the rotational movement of the drive shaft in drive relation thereto. Such a positioning and arrangement of the wobble plate mechanism has a number of disadvantages. First, it is difficult, particularly in an opposed piston, two cycle engine to open exhaust ports before the opening of intake ports, and to close the exhaust ports before the closing of the intake ports, which is necessary in order to clean the cylinder of residual exhaust gases. When a large number of pistons in a multiple cylinder engine are connected to a single wobble plate, it is practically impossible to control the firing order of the engine with a minimum of engine vibration and associated noise. When all pistons are connected to a single wobble plate, it is likewise very difficult to control the firing sequence angle as such angles are controlled by the movement of the common wobble plate. An engine having such a wobble plate construction is illustrated in U.S. Pat. No. 4,169,436, dated Oct. 2, 1979 and shows a plurality of cylinders mounted in circumferentially spaced relation about the longitudinal axis of a drive shaft and having opposed pistons therein connected to a wobble plate adjacent each end of the cylinders for rotating the drive shaft.
Another example is shown in U.S. Pat. No. 3,196,698, dated July 27, 1965 in which an internal combustion engine has a crankshaft and a plurality of cylinders mounted in circumferentially spaced relation about the crankshaft with pairs of opposed pistons mounted in such cylinders. A pair of wobble plate linkages are positioned adjacent each of the ends of the cylinders thereby providing four (4) wobble plate arrangements with each wobble plate arrangement being driven by three (3) pistons through associated connecting rods.
In a wobble plate mechanism, the wobble plate oscillates between two inclined positions and also rotates simultaneously about two intersecting axes. The wobble plate mechanism normally has three (3) degrees of freedom as an independent rotational degree of freedom is provided about the longitudinal axis of a link between two joints, one joint being at the connection of a linkage to the piston and the other joint being a connection of the linkage adjacent the wobble plate. Ball joints may be utilized as a joint for a linkage at the piston and for the joint for the connection of the linkage to the wobble plate.
A related motion which is similar to that of the so-called wobble plate motion is obtained by a so-called Z-crank convertor. A Z-crank convertor is obtained by a pair of spaced opposed base members or blocks axially aligned with each other. Each base member or block has an inclined thrust bearing face with the inclined bearing faces being in an opposed spaced relation to each other.
Heretofore, it has been complicated, time consuming, and expensive to replace defective or worn pistons, cylinders, and connecting linkages for drive shafts or the like in reciprocating piston type engines or machines. Normally, a single-block type engine body is used and it has been necessary in order to obtain access to the pistons to remove covers or heads from the engine block which exposes all of the cylinders and pistons in order to remove or repair a single piston or cylinder.
Additionally, previous Z-crank convertor mechanisms provided between reciprocating pistons and a rotating drive shaft, have utilized a relatively large number of freedoms of movement in the linkage such as, for example, a pair of ball joints between the piston and the associated Z-crank mechanism. It is difficult to provide suitable lubrication for ball joints and to minimize any excessive leakage of the lubrication from such ball joints.